Method of making unitary magnetic pole pieces



METHOD OF MAKING UNITARY MAGNETIC POLE PIECES I Filed April 2, 1949 S p T953 w. A. FLETCHER EI'AL 2 Sheets-Sheet l Ir 1 l L P 29, 1953 w. A. FLETCHER ET AL 2,653,376

METHOD OF MAKING UNITARY MAGNETIC POLE PIECES Filed April 2, 1949 2 Sheets-Sheet 2 W #7- roe/vars Patented Sept. 29, 1953 METHOD OF MAKING UNITARY MAGNETIC POLE PIECES William A. Fletcher, Daleville, and Carl L. Clevenger, Anderson, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application April 2, 1949, Serial No. 85,146 2 Claims. (Cl. 29-1555) This invention relates to pole shoes for dynamo electric machines and its object is to provide a method and apparatus for making, without machining operation, a pole shoe having a pole face portion of the desired shape and a field coil receiving shank whose side and end surfaces are spaced inwardly from the side and ends of the face by bending afiat blank of soft steel into arcuate shape and by causing the blank to be forced by a die which engages its concave surface against a die having surfaces which engage those portions of the convex surface of the blank which are adjacent the periphery thereof, the central portion of the convex surface spaced from the periphery being unsupported by reason of a hole in the second die into which a part of the blank is forced to provide a pole piece shank while the portions between the dies are shaped to provide a flange which extends from the shank portion to form peripheral portions of the pole face. The pole shoe thus formed is squeezed between sizing dies which render the concave and con- -vex surfaces now nearly concentric and determine the radial distance between them and which complete the shaping of flange portions.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred emobdiment of the present invention is clearly shown.

In the drawings:

Fig. 1 which is a sectional view on line l-l of Fig. 2, and Fig. 2 which is a sectional view on the line 22 of Fig. 1, show the dies which shape a blank into approximately the shape required for a pole shoe.

Fig. 3 is a view of the upper die member taken on the line and in the direction of arrows 3, 3 of Fig. 2.

Fig. 4 is a view of the lower die member taken on the line and in the direction of arrows 4, 4 of Fig. 2.

Fig. 5 is a view ona larger scale than the preceding figures showing, in section, the lower die member and in end elevation the upperdie member and between them, aformed pole shoe indicated by dot-dash line.

Fig. 6 drawn to the same scale as Fig. 5 is a fragmentary end view of the coining dies with a shaped pole shoe between them.

Figs. 7 and 8 are plan and end views, respectively, of a blank to be used in forming the pole shoes.

Figs. 9 and 10 are plan and end views, respectively, of a blank after being bent into arcuate 2 shape preparatory to shaping by the dies shown in Figs. 1 to 5.

Fig. 11 is an end view of the pole shoe after being shaped by the dies shown in Figs. 1 to 5.

Fig. 12 is an end view of the pole shoe after being sized by the dies shown in Fig. 6.

Fig. 13 is a view in the direction of arrow [3 of Fig. 12.

A blank of the shape shown in Figs. 7 and 8 is cut from a steel bar and is bent into arcuate form as shown in Figs. 9 and 10 and a central hole 2| is formed therein by a punching operation. The convex face of the blank has approximately the curvature of the inner cylindrical surface of the field frame to which the pole shoe is to beattached. The concave face of the blank has approximately the curvature of the pole face required for the armature that is to rotate within that field frame.

The next operation is performed upon the blank by dies 23 and 43, shown in Figs. 1-5. Die 23, formed from a cylindrical block of metal, has a cylindrical concave surface 24 whose axis of ourvature is represented by point Cl (Fig. 5), whose radius is H and whose subtended angle is a]. The surface 24 is midway between two like cylindrical, concave surfaces 25 whose axis of curvature is represented by point C2, whose radius is 1'2 and whose subtended angle is a2. Through the surface 24, the die 23 has a hole 26, which determines the shape of' the shank 22 (Figs. 5, 11-13) of the pole shoe. The surfaces 25 are close to the sides of hole 26. The die 23'is received by a cylindrical bore in a plate 2! which screws 28 attach to a plate '29 retained'upon the base 30 of a hydraulic press b clamps 3| which screws 32 attach to the base. Plate 21 has a cylindrical surface Z'Iaupon which the blank is received as it is pushed upon the die 23, and a cylindrical surface 21b for receiving the swaged pole shoe as it is pushed away from die 23. Downwardly inclined surface 210 directs the pole shoe into a container. Die 23 rests upon a spacer disc 33 having a central hole 34 for receiving a knock-out pin 35 guided by the plate 29 and adapted to be moved upwardlyby .a mechanically operated rod 36 so as to engage an'ejector bar 31 received by hole 26. The angular position of parts 23 and 33 is determined by a key 38 received by a slot 39 in plate 21 and engaging flats guided by parts 33 and 23. Screws 40 threaded through plate 27 engage flats 4| on die 23 to secure it firmly in position. Plates 2! and 29 support pilot rods 42. The head of a hydraulic press which actuates the die 43 receives screws 5| which seface it. surfaces 16. Die it provides surfaces '11"? oblique- 3 cure clamps 52 which fix a plate 53 to the head. Screws E l connect plate 53 with a plate 55 for supporting a block 55 to which the die 33 is attached by clamps iii and screws 58. The block 56 is provided with a groove 59 in which the die 33 is fastened. Die 43 supports a pilot pin 60, the head of which engages the block 56. A key 6! received by a slot 62 in block 56 and by a notch in the flange of block 56 locates the latter block in such position that the axis of the cylindrical die 43, whose axis of curvature is represented by point 03 in Fig. 5, will be in vertical alignment with the axes of C! and C2 of the surfaces 2d and 25 respectively of die 23. Plate 53 has clearance holes 63 and plate 55 has bushings $4 for receiving the pilot rods 42.

While the dies are separated, the blank shaped as shown in Figs. 9 and 10, is placedcpnyex side,

down upon the surface 24 of die 23 and centrally thereof so that the hole 21 therein will be approximately in alignment with the pin 68 which has a rounded lower end. The upper die 43 is lowered against the blank and the pin 653 enters'the hole H to center it accurately. The pressure'applied by the die is sufficient to cause the central portion ofthe blank extending between the sides and the ends of the hole 25 to be forced in the hole to form the shank 22. of the pole shoe while the supported portions extending beyond the sides of hole 26 are squeezed between the dies to cause.

portions of the flanges, this difference being de-.

termined by the relation of the surfaces of the die s'23 and 3. The thickness at'ar may be, for example, V as required by thejpole shoe de signer. flange portions between the regions a, those pore tionsare shaped to provide thickness which inture of surfaces '14 and 15 become coincident so that the convex and concave faces of the pole shoe become more nearly exactly concentric. At the same time the pole tip portions of the shoe which the side flange portions 2 provide are compressed into wedge-like shape. This deformation causes a slight flow of'the metal which so conditions the tip portions that they do not spring back (upwardly in Fig. 6) when the die pressure is relieved. Thus the outer plane surfaces of .thepole face remain tangent to the concave cylindrical'surfaces thereof.

After the sizingoperation the central hole 2! in the pole shoe is-tapped to receive a screw for attaching the convex surface of its shank 2i to the inner cylindrical surface of a field frame of a dynamo electric machine after a field coil has. been placed around its shank.

While. the embodiment of the present invention asherein disclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted. I

What is claimed is as follows: f

1. In the method of making a unitary magnetic if pole piece, having a shank portion'thereon", from a flat blank of soft steel, the steps comprising,

bending a flat blankof soft steelto anarcuate" form, simultaneously piercing a central hole therein, centering the blank in a die'byfplacingii' a centering rod through saidholejholdinglthe peripheral portions only of the blank'by supporting the blank at its peripheral portions only j thereof, swaging and drawing inetarfrong said supported blankinto the central portionthereof f forming a shank, removing the thus formed blank, and finally coining the opposed redu ced'fi from a single-pieceof flat soft steeLthe steps comprising; bending a fiat blank of soft steel In order to avoid cracking of the end creases toward the middle. to about ee, for I example.

When the press head so is raised therod as.

is raised tocause pin 35 and bars? to risetov lift the shoe above the die 23 to permit pushing the shoecut upon the surfaces 27b and 2'50 of J plate-21,; J I A w The pole, shoe, is then placed, between sizing dies Wand ll supported by the head and bed. respectively, of another hydraulic press, not.

shown, The die H isattached tov ablock '52 carried by the press head, ,Die it has a concave surface l i'for receiving the convex face of the polte shoe and die if ,has a convex surface 15 adapted toengagethe concave face of the pole shoe. Surfacel'fi 'subtends angle at from point .1 C4 which represents the axis of curvature of sur- Surface "i5 merges with tangent plane to surfaces 75. When die H is'lowered completely to a position which the radial thickness outer portions of the arcuate portion thereof, to taper them outwardly from the eenter.

2. The method of making a unitary magnetic, pole shoe having a shank portion thereon adapted", toreceive a coil-wherein said shoe is formed into an arcuate'form, clamping said arcuatebla'nk adjacent the peripheral portions only thereofmf while permitting the central portion thereof to remain unsupported, swaging and drawingi said blank in such held and supportedposition and" thus causing metal to flow into the unsupporte' portion and thereby-thicken said portion into a shank, and then coining -the opposedjre'ducedi" outer portions of the arcuate'portion thereof to taper them outwardl fromthe'center, 1 WILLIAM A. FLETCHER CARL L. CLEVENGER References ones in the h of this p 'at nt" UNITED STATES PATENTS 

